Apparatus for constructing magnetic cores



Oct. 18, 1960 R. J. OTTENHEIMER EIAL 2,956,755

APPARATUS FOR CONSTRUCTING MAGNETIC CORES 6 Sheets-Sheet 1 Filed June 3. 1957 flttorney' Richard J Ozften/zemer PoZZand 1/. Gaumer BY I Oct. 18, 1960 R. J. OTTENHEIMER ETAL 2,956,755

APPARATUS FOR cousmuc'rmc MAGNETIC comes Filed June 3. 1957 5 Sheets-Sheet 2 lll l l lL l IN V EN TORS.

Eda/1am, J Owen/mime? gyoZZmvd If 642077287 APPARATUS FOR CONSTRUCTING MAGNETIC CORES Richard J. Ottenheimer, Visalia, Calif., and Rolland V. Gaumer, Zanesville, Ohio, assignors to McGraw-Edison Company, Milwaukee, Wis., a corporation of Delaware Filed June 3, 1957, Ser. No. 663,230

2 Claims. (Cl. 242 -9) This invention relates to magnetic cores for stationary induction apparatus and in particular to apparatus for constructing magnetic cores of the so-called skew type wherein successive convolutions of wound magnetic strip are staggered in a regular and uniform manner to provide slanting faces in the winding legs and yokes.

Three phase electrical transformers are well known wherein three rectangular, skew type magnetic cores formed of continuous magnetic strip are arranged at 120 degrees to each other so that the yoke portions form the sides of a triangle and the winding legs of adjacent cores pass through the window of an electrical winding. In each rectangular core the edges of the lamination turns in both the straight leg portions and the yoke portions are stepped, or staggered, to provide slanting faces, and the slanting faces of the straight leg portions are in edge-to-edge contact where they pass through the conducting winding to provide a good space factor within the winding window and to assure minimum reluctance in the direction in which magnetic flux transfers from core to core.

It is an object of the invention to provide novel apparatus for constructing magnetic cores of the skew type. It is a further object of the invention to provide such apparatus which greatly reduces the time required to con struct skew type cores in comparison to prior art apparatus. Still another object of the invention is to provide such apparatus wherein it is unnecessary to reverse the driving means in order to return the apparatus to its starting position wherein it is ready for constructing another core. A still further object of the invention is to provide such skew core constructing apparatus which assures that the successive turns are staggered in a uniform and symmetrical manner.

These and other objects and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawing wherein:

Fig. 1 is a perspective view schematically illustrating the novel apparatus of the invention;

Fig. 2 is a view illustrating a skew type magneticcore constructed in the apparatus of Fig. 1 and having a portion broken away to illustrate the different width magnetic ribbons;

Fig. 3 is a vertical sectional view through the magnetic ribbon guiding means of the invention taken on line 33 of Fig.

Fig. 4 is an auxiliary view illustrating the means for adjusting the drag on the magnetic ribbon as it is being wound; and,

Fig. 5 is an end view of the ribbon guiding means shown in Fig. 3 and having portions broken away to better illustrate the construction.

Referring to the drawing and particularly to Fig. 2, a rectangular magnetic core of the skew type comprises a plurality of convolutions 11 of continuous magnetic ribbon wound on a rectangular mandrel 12 and staggered, or stepped, to provide slanting faces 13 on States Patent 0 Patented Oct. .18, 1960 both the winding legs and the yokes. The illustrated core 10 is wound of two different width magnetic ribbons,

and in any leg or yoke of the core the edges of all of the turns on one side of the core are in a common plane at an acute angle to the axis of mandrel 12. Three such rectangular, skew type magnetic cores 10 are arranged at degrees to each other with the yokes of the three cores forming the sides of a triangle to construct a three phase transformer, for example of the type illustrated in US. 2,401,952 in the name of Walter R. Mayberry,

and the slanting faces 13 of the straight leg portions of adjacent cores are in edge-to-edge contact where they pass through the window of a conductive winding. In order to provide maximum efficiency in the utilization of the space within the winding window and to facilitate transfer of magnetic flux from core to core, it is desirable that the staggering of the edges of the turns 11 of magnetic ribbon be uniform to assure intimate contact, or close engagement, 'between the adjacent winding legs. Uniform and symmetrical staggering of the convolutions is obtained in skew type magnetic cores constructed with the apparatus shown in Fig. 1 wherein it is schematically represented that rectangular mandrel 12 is rigidly allixed by suitable means to a drive shaft 16 which is rotatably supported in suitable bearings 17 and driven by motor 18 through speed reduction gearing (not shown) enclosed within housing 20. In the construc tion of a skew type magnetic core, the end of a continuous magnetic strip 21 is aflixed by means (not shown) to mandrel 12, and mandrel 12 is rotated by motor 18 to spirally wind the magnetic ribbon 21 on the rectangular mandrel 12. The magnetic ribbon 21 is fed between tensioning rollers 23 and 24 urged toward each other by suitable resilient means illustrated as a spring 25 to assure thatthe turns are tightly wound on mandrel 12, and the magnetic ribbon 21 is shifted laterally as it is being wound to step the convolutions in a regular and uniform pattern. Rotatable guide spools 26 and 27 disposed on opposite sides of magnetic ribbon 21 are mounted on a guide carriage 28 supported by means (not shown) to permit reciprocation perpendicular to the direction the magnetic ribbon 21 is being fed, i.e., parallel to the axis of mandrel 12.

A vertical rod 29, having one end protruding into an elongated aperture 30 in guide carriage 28, is affixed at its other end to a threaded follower nut 32 releasably engaging a lead screw 33 which is driven in synchronism with mandrel 12 from drive shaft 16 through means schematically represented as a belt 34 and suitable reduction gearing (not shown) enclosed within housing 37. The axis of lead screw 33 is parallel to the axis of mandrel 12, and the longitudinal axis of elongated aperture 30 is perpendicular to the axis of lead screw 33. The rod 29 slidable within elongated aperture 30 comprises interconnecting means between follower 32 and carriage 28 permitting relative movement therebetween in a direction perpendicular to the axis of lead screw 33 but preventing relative movement therebetween in a direction parallel to the axis of lead screw 33. The follower nut 32 is normally urged into engagement with lead screw 33 by a spring 38, and if the operator pulls handle 39 attached to follower nut 32 in the direction shown by the dotted line arrow to move vertical rod 29 into the opposite end of elongated aperture 30, the follower 32 is moved, against the force of spring 38, out of engagement with lead screw 33 to permit return of the guide carriage 28 to its initial position without reversing the motor 18. It is thus unnecessary to mechanically drive the carriage 28 back to the starting position wherein it guides the initial turn of magnetic ribbon 21 onto mandrel 12 each time another magnetic core '10 is to be constructed, and

consequently the construction time is materially reduced in comparison to prior art core winding apparatus.

As best shown in Figs. 3-5 which illustrate a preferred embodiment of the invention, the magnetic strip 21 is fed between a pair of guide rollers 40, thence between a first pair of guide spools 26 and 27 disposed on opposite sides of strip 21, between upper and lower tensioning rollers 23 and 24, between a second pair of guide spools 26 and 27 mounted on guide carriage 28, and thence between another pair of guide rollers 41 before being wound on mandrel 12. Each guide spool 26, 26, 27 and 27' has a circumferential groove 46 for receiving the magnetic strip 21. The guide spools 26 and 26 on one side of the magnetic strip 21 rotate freely about bearings 47 circumjacent thumb screws 50. The thumb screws 58 are engaged within threaded apertures in members 53 of inverted-T shaped cross section which are positioned within dovetail grooves 54 (only one being shown) in upstanding transverse support members '56 and 60 on carriage 28. The position of guide spools 26 and 26' on one side of magnetic strip 21 is not changed during the construction of the skew type magnetic cores 10, but in order to guide the different width magnetic ribbons, the guide spools 27 and 27' on the side of the magnetic strip 21 opposite the spools 26 and 26' are provided with locking means which facilitate their easy removal and installation in an adjacent position. Each guide spool 27 and 27 is freely rotatable about a vertical pin 57 which is adapted to be inserted within any one of a plurality of apertures 59 (only one being shown) provided in upstanding transverse supporting members 56 and 60 of guide carriage 28. The apertures 59 are spaced at different distances from the threaded apertures 51 wherein the guide spools 26 and 27 are disposed. A circumferential groove 62 of arcuate cross section provided adjacent the lower end of each pin 57 is adapted to receive a ball 63 resiliently urged by a spring 64 disposed in a horizontal aperture 65 registering with the aperture 59 to releasably secure pin 57 within aperture 59. A screw 66 threaded within aperture 65 permits adjustment of the force with which spring 64 urges ball 63 into circumferential groove 62. It will be apparent that when a different width magnetic ribbon is to be wound, it is only necessary for the operator to manually withdraw pins 57 carrying guide spools 27 and 27 from apertures 59 and to insert the pins 57 into the apertures 59 appropriate for the width of magnetic ribbon to be wound.

Screws 69 extending through vertical end plates 70 of guide carriage 28 and engaged within threaded apertures in the transverse support members 56 and 60 secure the end plates 70 to the support members 56 and 60. The end plates 70 have inwardly projecting portions 71 provided with clearance holes 72 for receiving bolts 73 which carry circumferentially grooved rollers 74 freely rotatable about suitable bearings 76 circumjacent bolts 73 and supported on bolts 73 by nuts 77. The arcuate edges 80 of an elongated, horizontal support plate 81 extend into arcuate-in-cross-section circumferential grooves 79 in the rollers 74 to mount the carriage 28 upon horizontal plate 81 for reciprocation in a direction parallel to the axis of lead screw 33, i.e., in a direction perpendicular to magnetic strip 21. Horizontal support plate 81 is aflixed by screws 82 to transverse frame members 83 which are secured to end frame members 84 by studs'85.

Lead screw 33 is rotatably supported within suitable bearings 87 in end frame members 84, and the means for driving lead screw 33 in synchronism with the rotation of mandrel 12 includes a toothed gear 88 affixed to lead screw 33 and engaging a toothed gear 89 supported on a shaft 91 extending through suitable bearings (not shown) in end frame members 84.

Threaded half nut follower 32 has teeth complementary to lead screw 33 and is formed at its upper end with a trapezoidal shaped portion 94 (see Fig. which is freely slidable within an elongated dovetail groove 95 in a follower retaining block 97 to permit reciprocation of follower 32 relative to block 97 in a direction parallel to the axis of lead screw '33. A generally trapezoidal shaped portion 98 on the upper end of follower retaining block 97 (see Fig. 3) fits within a dovetail groove 99 formed by a pair of elongated, trapezoidal shaped retainer guides 100 secured by screws 101 to horizontal support plate 81 to permit reciprocation of follower retaining block 97 carrying follower 32 relative to carriage 28 in a direction perpendicular to the axis of lead screw 33. An elongated aperture 102 is provided in follower retainer block 97 in register with an elongated slot 103 provided in horizontal support plate 81, and the longitudinal axis of the registering slots 102 and 103 is parallel to the axis of lead screw 33. Vertical rod 29 described hereinbefore extending through registering apertures 102 and 103 and threaded at one end to follower 32 and fitting at its opposite end within elongated aperture 30 in the bottom face of an end plate 70 of carriage 28 interconnects carriage 28 to follower 32 and causes carriage 28 to reciprocate with follower 32 in a direction parallel to the axis of lead screw 33 when motor 18 is energized.

The aperture 30 receiving vertical rod 29 is elongated in a direction perpendicular to the axis of lead screw 33 to permit manual movement of follower retainer block 97 and follower 32 carried thereby in a direction perpendicular to the axis of lead screw 33 and thus permit disengagement of follower 32 from lead screw 33 when the operator manually pulls handle 39. The follower 32 is normally urged into engagement with lead screw 33 by spring 38 hearing at one end against follower retainer block 97 and its opposite end against the bottom wall of a cylindrical compartment 109 in a transverse frame member 83. Spring 38 is circumjacent handle 39 which threadably engages follower retaining block 97 and extends through compartment 109 and a clearance hole in transverse frame member 83. If the operator pulls on a knob 111 secured to handle 39, follower retainer block 97 and follower 32 carried thereby are moved in a direction to slide the trapezoidal shaped portion 98 on block 97 within the dovetail groove 99 formed by guides 100, and to also move vertical rod 29within elongated aperture 30, and thus disengage follower 32 from lead screw 33. It will be apparent that at the end of the operation of winding the magnetic strip 21 into a closed core 10, when the carriage 28 is at an extreme position wherein the follower nut 32 is adjacent one end of the lead screw 33, the operator need only pull knob 111 on handle 39 to disengage follower nut 32 from lead screw 33 and manually return guide carriage 28 to its initial position ready for constructing another closed core 10, and that it is thus unnecessary to reverse motor 18 to return guide carriage 28 to starting position.

In order to assure that the magnetic strip 21 is wound tightly on mandrel 12, a drag is placed on magnetic strip 21 by tensioning rollers 23 and 24. Upper tensioning roller 23 comprises a cylindrical member 112 supported at its end on suitable ball bearings 113 circumjacent a shaft 114, and thus upper tensioning roller 23 is freely rotatable. Lower tensioning roller 24 includes a cylindrical member 115 rigidly affixed to a shaft 116 by set screws 117, and the shaft 116 is rotatably journalled in ball bearings 120 carried within suitable openings in end plates 70 of guide carriage 28.

A retarding torque is applied to shaft 116, carrying lower tensioning roller 24, by a brake band122(see Fig. 4). Brake band 122 includes two arcuate brake shoes 123 having suitable friction material members 124 on the inner arcuate periphery thereof urgedinto engagement with a drum 127 secured to shaft 116 by keys 128 fitting within keyways in the inner periphery ofdrum 127 and in the outer peripheryof shaft 116. A screw 129 extending through both arcuate brake shoes 123 and threadably engaging one endplate 70 hinges the'brake shoes 123 together. Means for varying the retarding torque on shaft 116 includes a threaded stud 130 connected to a radially extending arm 133 on one brake shoe 123 by a pin 134, a helical spring 136 circumjacent stud 130 and compressed between radial arm 133 and a radial arm 138 on the other brake shoe 123 and urging the brake shoes apart, a helical spring 140 circumjacent stud 130 and bearing against radial arm 138, and a hand nut 141 threaded on stud 130 and compressing spring 140 against radial arm 138. It will be apparent that tightening nut 141 will urge brake shoes 123 closer together and increase the pressure with which frictional material members 124 are held against drum 127 to thereby increase the drag of brake band 122 on shaft 116 and thus increase the retarding tension on magnetic strip 21 as it is being wound on mandrel 12.

Upper tensioning roll 23 is resiliently urged toward lower tensioning roll 24. The ends of shaft 114 carrying upper tensioning roller 23 fit within suitable apertures in rectangular blocks 144 and are affixed thereto by keys 145. The rectangular blocks 144 are slidable vertically within guideways 146 in the end plates 70 of guide carriage 28. Bolts 150 extending through clearance holes adjacent the ends of an elongated tensioning bar 151 threadably engage the rectangular blocks 144, and springs 153 circumjacent bolts 150 and compressed between the blocks 144 and the tension bar 151 resiliently urge blocks 144, and upper tensioning roller 23 carried thereby, in a downward direction when tensioning bar 151 is forced downward. An elongated aperture 152 provided through tensioning bar 151 freely receives a circular cam 154 having a radial extending handle 155 and being pivoted within aperture 152 about a pin 157 extending through the center thereof. Pivot pin 157 extends through transverse support plates 158 disposed on opposite sides of tension bar 151 and secured at their ends by means (not shown) to the end plates 70 of carriage 28. Points along a cam slot 159 formed in cam 154 are at varying distances from the center of circular cam 154, and a follower pin 160 within the cam slot 159 extends through the walls of tensioning bar 151 defining the elongated groove 152. As cam 154 is turned by manually rotating cam handle 155 counterclockwise to the position shown in Fig. 3, follower pin 160 and tensioning bar 151 are urged downwardly, thereby compressing springs 153 and resiliently urging upper roller 23 toward lower roller 24. It will be apparent that if the operator turns cam handle 155 to the vertical position, tensioning bar 151 will be raised and permit upward movement of upper tensioning roller 23 relative to lower tensioning roller 24 and thus allow the operator to feed magnetic strip 21 freely between tensioning rollers 23 and 24.

While only a single embodiment of the invention has been illustrated and described, it will be apparent that many modifications and variations thereof will be apparent to those skilled in the art, and consequently it is intended in the appended claims to cover all such modifications and variations which come within the true spirit and intent of the invention.

It is claimed:

1. Apparatus for constructing closed, wound strip magnetic cores having the turns staggered to form slanting faces in the yokes and legs thereof, comprising, in combination, a rotatable mandrel, a frame having a horizontal support plate elongated in a direction parallel to the axis of said mandrel, a carriage, means including a plurality of rollers rotatably supported on said carriage and engaging the elongated sides of said support plate for mounting said carriage for reciprocation parallel to the axis of said mandrel, means on said carriage including a pair of spaced apart guide spools adapted to receive magnetic strip therebetween for guiding magnetic strip as it is wound onsaid mandrel, a lead screw rotatably supported with its axis parallel to the axis of said mandrel, means for rotatably driving said mandrel and said lead screw in synchronism, a follower releasably engaging said lead screw, spring means for resiliently urging said follower into engagement with said lead screw, means for supporting said follower on said carriage, said last-named means permitting movement of said follower relative to said carriage against the force of said spring means in a direction perpendicular to the axis of said lead screw but preventing movement of said follower relative to said carriage in a direction parallel to the axis of said lead screw, and means on said carriage including a pair of rotatably mounted rollers having parallel axes and adapted to receive magnetic strip therebetween for exerting a retarding effect on said magnetic strip as it is wound on said mandrel, said retarding means also including spring means for resiliently urging said rollers toward each other to bear in approximately line contact on opposite faces of said magnetic strip and being instantaneously releasable to permit insertion of different width magnetic strip between said rollers, and brake means on said carriage for exerting a retarding torque on one of said rollers and being manually adjustable to vary said retarding torque, one of said guide spools being adjnstably mounted on said carriage to permit reception of different width magnetic strip within said strip guiding means.

2. Apparatus for constructing closed, wound strip magnetic cores having the turns stepped in a uniform and symmetrical pattern to provide slanting faces in the yokes and winding legs thereof, comprising, in combination, a rotatable mandrel, a carriage mounted for reciprocation parallel to the axis of said mandrel, means on said carriage for guiding magnetic strip to be wound on said mandrel, a lead screw having its axis parallel to the axis of said mandrel, means for rotating said lead screw and said mandrel in synchronism, a member slidably supported on said carriage for movement relative to said carriage in a direction perpendicular to the axis of said mandrel, a follower releasably engaging said lead screw and being slidably supported on said member for movement relative to said member in a direction parallel to the axis of said mandrel, interengaging means between said follower and said carriage permitting relative movement therebetween only in a direction perpendicular to the axis of said mandrel, and resilient means urging said follower in a direction perpendicular to the axis of said mandrel into engagement with said lead screw, and means on said carriage including a pair of rotatably mounted tensioning rollers having parallel axes and adapted to receive said magnetic strip therebetween for exerting a retarding force on said magnetic strip as it is wound on said mandrel, said retarding means including means for resiliently urging said tensioning rollers toward each other to bear in approximately line contact on opposite sides of said magnetic strip means for releasing said rollerurging means to permit insertion of different width magnetic strip between said rollers, and brake means on said carriage for exerting a retarding torque on one of said rollers and being manually adjustable to vary said retarding torque.

References Cited in the file of this patent UNITED STATES PATENTS 1,263,419 James Apr. 23, 1918 1,380,837 Replogle June 7, 1921 2,643,068 Harris June 23, 1953 FOREIGN PATENTS 984,898 France Feb. 28, 1951 

